1. Field of the Invention
The present invention relates to a thin-film manufacturing method and apparatus for depositing a thin film on a substrate to be deposited, and, in particular, relates to a thin-film manufacturing method and apparatus used for a recording device (specifically, hard disk device) or the like mounted in an information recording apparatus of information processing equipment such as a computer and also mounted in a consumer product.
2. Description of the Related Art
Recently, recording capacity of an information recording device is increasing, as an information volume treated by information processing equipment such as a computer is increasing and the size of the information processing equipment is reducing. Along with this trend, a recording capacity required for a magnetic recording medium used in the information recording device is increasing continuously. To increase the recording capacity of the magnetic recording medium for improving recording capability, it is necessary to reduce a distance between a read-write element of a magnetic head and a magnetic layer of the magnetic recording medium, that is, a magnetic spacing, to the limit. The magnetic spacing is determined by a thickness of a protection layer of the magnetic head, a floating amount of the magnetic head, thicknesses of the protection layer and a lubricating layer of the magnetic recording medium, and the like.
One subject for developing the magnetic recording medium is to reduce the protection layer thickness. The protection layer of the magnetic recording medium typically employs DLC (Diamond-Like Carbon), which is formed mainly by a chemical vapor deposition (hereinafter, CVD) method or the like. The thickness of the protection layer of the magnetic recording medium has been reduced down to approximately 3 nm, but further reduction is required in the future.
As an alternative method of forming the DLC protection layer, a filtered cathodic arc method (hereinafter, FCA) and its improved method are proposed (see, e.g., Japanese Patent Laid-Open No. 2001-209929). In the FCA method, only carbon ions generated by arc discharge are selected using a mass filter and guided to a substrate to be deposited to form a DLC film. In the above described improved method, the carbon ions are produced by generating a gas-phase plasma instead of the arc discharge. There is also proposed a method of capturing a large amount of particles generated in the FCA method on the way of an ion transfer path (see, e.g., Surface and coatings 163-164 (2003) P. 368-373).
To reduce the thickness of the protection layer of the magnetic recording medium, it is necessary to solve conventional problems regarding an initial growth layer as follows.
In the magnetic recording medium, a protection layer including DLC is formed on a magnetic layer. When the protection layer is formed on a boundary surface of an under layer made of a different material in this manner, plural nuclei are first generated in the state of dots on the under layer boundary surface, and then these plural nuclei grow to form island shapes, in the initial growth process. Up to this step, the layer is called an initial growth layer and the thickness thereof is considered to be approximately 0.5 to 1.0 nm. These island-like nuclei are gradually connected with one another to form a uniform normal layer. The initial growth layer is inferior to the normal layer in material fineness. As described above, the thickness is very small as approximately 3 nm in the case of the protection layer of the magnetic recording medium. For example, if the thickness is reduced down to two third of the current thickness, that is, approximately 2 nm, and the thickness of the current initial growth layer is assumed to be approximately 1 nm, a half of the protection layer is the initial growth layer which is inferior in the material fineness. Such a layer cannot satisfy corrosion resistance and abrasion resistance required for the protection layer.
Meanwhile, when the thin film as described above is formed, there exist mainly two kinds of mechanisms. One is film deposition with radicals, and the other is film deposition with ions. In the former case of the radical film deposition, the film is formed by so-called surface reaction, which results in the above described island-like growth. This is because the radicals do not have large energy. On the other hand, in the latter case of the ion film deposition, the ions are driven into the surface of the substrate to be deposited by energy provided by an electric field or the like. As a result of a so-called ion bombardment effect, the film is formed as precipitated under the surface. Specifically, since the ion film deposition does not include an initial growth layer such as the island-like growth, application of an appropriate energy allows to form a fine film in which a sp3 structure component of a diamond structure is rich in the case of the DLC, for example. If the ions are used for film deposition, it is possible to reduce the thickness of the protection layer, since the protection film is densified.
However, in a typical plasma CVD method, generated plasma includes a large amount of radicals in addition to the ions. Accordingly, this method does not provide a pure ion film deposition but provides a mixture film deposition state in which the ion film deposition and the radical film deposition exist together. Since such results in forming the initial growth layer, it was difficult to reduce the film thickness. Further, the FCA method is already known to be a method of forming a DLC layer which does not include the initial growth layer as a result of the pure ion film deposition. However, since a large amount of particles are generated by arc discharge, it has been difficult to apply the FCA method to the deposition of a protection layer of the magnetic recording medium.